Wellbore operations often utilize wellbore tools deployed on cables, including without limitation wirelines and slick lines. For example, well logging operations commonly utilize a logging tool deployed in the wellbore on an electric wireline. A common problem that occurs in these operations is that the cable gets stuck in the wellbore. Sticking of the cable, as opposed to the wellbore tool, often occurs due to being key-seated or differentially stuck. Key seated commonly refers to situations, such as in deviated wells, where the cable digs into the wall of the wellbore to a sufficient depth that the attached tool can no longer be moved in the wellbore. When the cable is differentially stuck, the wellbore pressure is greater than the formation pressure resulting in the cable essentially being sucked to the wellbore wall. The cable may penetrate into the wall or be stuck by virtue of the friction and drag of the cable on the wall.
Once stuck, the first objective is to free the tool as quickly as possible. Thus, the first step is to pull on the cable. However, this often results in the cable parting requiring that fishing operations commence. Fishing operations result in significant lost time and increased operation costs. Another solution in the past has been to run, or essentially free-fall, a bar or pipe sub over the cable to the tool. Unfortunately, while this method may free the cable, when the sub impacts the tool, the force of the impact detaches the wellbore tool from the cable. Again, this results in fishing operations.
Therefore, it is a desire of the present invention to provide a method and apparatus for releasing a cable stuck in a wellbore without detaching the connected wellbore tool.